This disclosure relates to a gas turbine engine fan section. More particularly, the disclosure relates to spacers used between circumferentially arranged fan blades in the fan section.
One type of gas turbine engine includes a fan section arranged at an inlet of the engine. The fan section includes multiple circumferentially spaced fan blades that must be designed to withstand ingestion of foreign objects during operation, such as bird strikes. The use of composite material for fan blades has become more prevalent to reduce engine weight and improve fuel efficiency. Designing a fan blade constructed from composite materials that performs during foreign object ingestion in a desired manner is challenging due to the reduced ductility of the composite materials as compared to conventional metal blades.
Designing fan blades for bird strike scenarios is challenging for at least two reasons. First, the fan blade must perform in a desired manner during the actual bird strike at the impact sight. Second, the fan blade is subject to high bending and twisting loads near the fan blade attachment location in response to the impact energy. The attachment locations are typically provided by hub slots that receive a root at a base of each fan blade. The root loads are especially damaging if the fan blade is rigidly constrained at the inner flow path. Some fan sections use spacers between the fan blades at the hub. High root loads can result in catastrophic separation of the fan blade from the hub, which is undesirable. For example, the rigid spacers can act as a fulcrum against which the fan blades act under bending and/or twisting loads, resulting in fracture and separation of the fan blades from their roots.